1. Field of the Invention
The present invention relates to a heat-sensitive adhesive label manufacturing device and a heat-sensitive adhesive label manufacturing method.
2. Description of the Related Art
Conventionally, in order to manufacture a heat-sensitive adhesive label capable of adhering to various products, there is used a method in which a heat-sensitive adhesive layer provided on one side of a heat-sensitive adhesive sheet is heated and thermally activated to exhibit adhesive properties. As means for thermally activating the heat-sensitive adhesive layer, there is generally used a well-known thermal head which is widely adopted in a thermal printer. By using the thermal head, it is possible to easily cause the heat-sensitive adhesive layer to exhibit the adhesive properties partially, and to cause an adhesive part and a non-adhesive part to exist next to each other relatively freely. Note that, in some cases, the heat-sensitive adhesive label having a surface on which characters, symbols, designs, etc. are recorded is obtained by providing a heat-sensitive coloring layer on the other side of the heat-sensitive adhesive sheet, and partially heating the heat-sensitive coloring layer to develop color.
In the conventional heat-sensitive adhesive label manufacturing device for manufacturing the heat-sensitive adhesive label, the thermal head is arranged at a position of being brought into contact with the heat-sensitive adhesive layer as described above, and a platen roller is arranged at a position of being opposed to the thermal head. The platen roller presses the heat-sensitive adhesive sheet against the thermal head, and functions to convey the heat-sensitive adhesive sheet by its rotation. Further, in such a heat-sensitive adhesive label manufacturing device, a discharge roller is arranged on a downstream side of the thermal head and the platen roller, that is, between the thermal head and the platen roller, and a discharge port for the heat-sensitive adhesive label.
If the heat-sensitive adhesive sheet is stopped immediately at the point in time when a rear end portion of the heat-sensitive adhesive sheet moves away from a position of being brought into contact with the platen roller, there may arise a problem that the heat-sensitive adhesive sheet is held at a position of being brought into contact with the thermal head, and thus the heat-sensitive adhesive layer adheres to the thermal head, and a problem that, even though the heat-sensitive coloring layer is not directly brought into contact with a heating portion of the thermal head, the heat-sensitive coloring layer develops unexpected color due to transmission of heat at the contact position between the heat-sensitive adhesive sheet and the thermal head or in the vicinity of the contact position. Therefore, in order to convey the heat-sensitive adhesive sheet further on the downstream side and to cause the same to fully move away from the thermal head, the above-mentioned discharge roller is provided, the heat-sensitive adhesive sheet having the rear end portion which has moved away from the position of being brought into contact with the platen roller. Owing to provision of the discharge roller, the thermally-activated heat-sensitive adhesive sheet is separated from the thermal head, and it is possible to prevent the heat-sensitive adhesive layer from adhering to the thermal head, and to prevent the heat-sensitive coloring layer from developing unexpected color. In addition, the discharge roller holds the heat-sensitive adhesive label while lightly sandwiching the same between a guide member and the discharge roller in the vicinity of the discharge port, and functions to allow a user to easily take out the heat-sensitive adhesive label with a small force.
However, there is a risk that the heat-sensitive adhesive layer partially peels off and the heat-sensitive adhesive that has peeled off adheres to and deposits in an outer peripheral surface of the discharge roller. In this case, there is a risk that the heat-sensitive adhesive that has deposited in the outer peripheral surface of the discharge roller adheres to the subsequent heat-sensitive adhesive labels and inhibits advance of the heat-sensitive adhesive labels.
Therefore, non-adhesive coating is performed on the outer peripheral surface of the discharge roller. In addition, JP 2005-1139 A (Patent Document 1) proposes that discharge rollers (rotating bodies) are axially situated at intervals and have a plurality of wheel-shaped small protrusions, and an outer shape of the wheel-shaped protrusions is formed into a star shape or a gear shape, to thereby reduce a contact area with the heat-sensitive adhesive sheet and to reduce an amount of adhesion of the heat-sensitive adhesive. Further, JP 2005-239202 A (Patent Document 2) proposes that by shifting a position of a discharge roller (conveyor roller) to a side of the platen roller, the heat-sensitive adhesive sheet is easily separated from the thermal head, and thus stress generated on a contact surface between the heat-sensitive adhesive sheet and the discharge roller is reduced, to thereby prevent the heat-sensitive adhesive from adhering to the discharge roller.
According to the invention described in each of Patent Documents 1 and 2, it is possible to prevent, to some extent, the heat-sensitive adhesive from adhering to the discharge roller. However, the degree of prevention is not satisfactory. For example, even though the amount of adhesion is small, the heat-sensitive adhesive adheres to the outer peripheral surface of the discharge roller due to peeling-off, etc. of the non-adhesive coating of the outer peripheral surface of the discharge roller by a frictional force, the non-adhesive coating continuously coming into contact with the heat-sensitive adhesive sheet in accordance with use for a long period of time. As a result, the adhering heat-sensitive adhesive strongly fixes on a heat-sensitive adhesive of a subsequent heat-sensitive adhesive sheet, to thereby peel off the heat-sensitive adhesive. Therefore, once the heat-sensitive adhesive starts to adhere to the outer peripheral surface of the discharge roller, thereafter an amount of deposition of the heat-sensitive adhesive increases acceleratingly.
When the heat-sensitive adhesive adheres to and deposits in the outer peripheral surface of the discharge roller as described above, the adhesive strength between the discharge roller and the heat-sensitive adhesive sheet increases, and there is a risk that satisfactory conveyance of the heat-sensitive adhesive sheet cannot be performed. Specifically, as illustrated in FIG. 11, there is a risk that a heat-sensitive adhesive sheet 23, which is moved from a thermal head 21 and a platen roller 22, is dragged by a heat-sensitive adhesive 25 adhering to an outer peripheral surface of each of discharge rollers 24, and is wound around an outer periphery of one of the discharge rollers 24. Further, as illustrated in FIG. 12, there is a risk that a path for the heat-sensitive adhesive sheet 23 between the discharge rollers 24 and a guide member 26 is blocked by the heat-sensitive adhesive 25 adhering to the outer peripheral surface of each of the discharge rollers 24, and jamming (paper jam) occurs. Therefore, it is necessary to frequently exchange the discharge rollers 24, and to perform cleaning for removing the adhering heat-sensitive adhesive 25. Further, when the heat-sensitive adhesive 25 having relatively small adhesive strength exerted at the time of thermal activation is used in order to reduce the adhesion of the heat-sensitive adhesive 25 to the outer peripheral surface of each of the discharge rollers 24, the heat-sensitive adhesive 25 cannot obtain sufficient adhesive strength with respect to an adherend having a rough surface, and the heat-sensitive adhesive 25 may become unusable.